An analysis by NSS Labs highlights that layering security devices rarely catches all attacks. The analysis found that products tended to fail to detect attacks in ways that appeared to be correlated across products. Companies need to carefully select technologies to derive the greatest benefits from overlapping security measures, expert says. Layering security measures typically protects systems better: Research by three University of Michigan graduate students in 2008 found that using multiple antivirus engines result in much better protection than using a single program. The average failure rate for endpoint protection products was 45 percent, using two programs together reduced it to 26 percent.”]
Source: https://www.darkreading.com/analytics/3-lessons-from-layered-defense-s-missed-attacks